Subject Mathematics

Grade 4th

Students` Learning Outcomes

  • Draw a right angle using protractor.
  • Draw acute and obtuse angles of different measures using protractor.
  • Draw an angle using protractor:
  1. Equal in measure to a given angle,
  2. Twice the measure of a given angle,
  3. Equal in measure of the sum of two given angles,

Information for Teachers

  • To draw an angle of 50° first draw a line segment angle will be draw at its one end.


  • Then place the protractor so that its zero line matches with your line segment and that the vertex is in correct place. Then put a little mark at the spot showing 50 degrees.
  • Take the protractor off and draw a line through your mark till vertex point.
  • During this lesson teacher should consult textbook wherein and whenever it is applicable.

Material / Resources

Writing board, chalk/marker, duster, geometry box, pencil, rubber, paper, textbook


  • Recall the drawing of vertical line by using set-squares.
  • Ask any of the students to repeat and then introduce another way of drawing it.



Activity 1

  • Say: “We can also use a protractor to construct a right angle.” Using the straight edge of the protractor, draw ray Description: C:UsersAamer computersDownloadsMath Symbols List (+,-,x,_,=,...)_filesray.gif on board, as;
  • Say: “We are going to construct a right angle with its vertex at point “A”. How should we place the central point of the protractor?” (Place the central point of the protractor on point “A” and the 0 line of the protractor on ray AB.)
  • Ask a student to demonstrate this at the board with the large wooden protractor.
  • Ask the students, which mark on the scale will represent right angle? (90°)
  • Ask a student to place a point on the board at the 90° mark, label it point C. remove the protector and draw a ray from point “A” through point “C”.
  • Ask: “How can we be ascertaining that we have constructed right angle?
  • (It measures 90° we can match against a known right angle, such as the corner of a page in a book).
  • What are the correct names for this angle?” (We can call it angle LA, angle BAC, or angle CAB).
  • Ask a student to write the angle names on the board as the others write them in their notebooks. Repeat the procedure by constructing additional angles.
  • Assign practice questions from book to work in individually.


Sum up / Conclusion
  • Right angle is of 90°.
  • Acute angle is greater than 0° and less than 90°.
  • Obtuse angle is between 90° and 180°.
  • Protractor is used to draw all angles.

Half or twice of an angle can be draw with protractor.


  • Ask them to draw 5 angles of their own choice and label them.
  • Any student come on board and demonstrates drawing of right angle.

Follow up

  • Assign activities from the textbook.
  • Draw three acute angles by using protractor and write each step?
  • Write the measurement of angles A 0B, A 0C, A0D, A0E, A0F from the following figure.


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